Dynamic riser string hang-off assembly

ABSTRACT

A dynamic hang-off assembly for supporting a riser string from an off-shore drilling rig including a dynamic tensioning system. The hang-off assembly includes a housing with a passage through the housing. The housing also includes a locking mechanism. The assembly further includes an adapter positionable within the housing passage. The outer surface of the adapter includes a profile. The riser string is also attachable to the adapter. The locking mechanism actuates to engage the adapter profile and secure the adapter to the housing. When the riser string is connected to the adapter and the adapter is secured by the housing, the riser string is supportable by the housing. The housing is also dynamically supportable by the dynamic tensioning system to dynamically support the riser string.

BACKGROUND

Offshore oil and gas operations often utilize a wellhead housingsupported on the ocean floor and a blowout preventer stack secured tothe wellhead housing's upper end. A blowout preventer stack is anassemblage of blowout preventers and valves used to control well borepressure. The upper end of the blowout preventer stack has an endconnection or riser adapter (often referred to as a lower marine riserpackage, or LMRP) that allows the blowout preventer stack to beconnected to a series of pipes, known as riser, riser string, or riserpipe. Each segment of the riser string is connected in end-to-endrelationship, allowing the riser string to extend upwardly to thedrilling rig or drilling platform positioned over the wellhead housing.

The riser string is supported at the ocean surface by the drilling rigand extends to the subsea equipment through a moon pool in the drillingrig. A rotary table and associated equipment typically support the riserstring during installation. Below the rotary table may also be adiverter, a riser gimbal, and other sensitive equipment.

During installation of the riser string, it may be necessary totemporarily move the entire drilling rig, such as for example when astrong storm is approaching. Before moving the rig, it is necessary topull up the entire riser. If the riser were left in place, movement ofthe rig would cause the riser string to damage the rotary table,diverter, gimbal, and other sensitive equipment. Pulling up each sectionof riser string takes a long time, adding cost to the overall drillingoperations. Additionally, there may not be enough time to pull theentire riser string before the rig needs to be moved.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIGS. 1A-1B show a drilling system;

FIG. 2 shows a perspective view of a dynamic hang-off assembly inaccordance with various embodiments;

FIG. 3 shows a side elevation view of the dynamic hang-off assembly ofFIG. 2;

FIG. 4 shows a top view of the dynamic hang-off assembly of FIG. 2;

FIG. 5A shows a side elevation view of the dynamic hang-off assembly ofFIG. 2 shown cutaway in a plane A-A of FIG. 4;

FIG. 5B shows a side elevation view of the detail area B of FIG. 5A; and

FIG. 6 shows a perspective view of the dynamic hang-off assembly of FIG.2 shown cutaway in a plane A-A of FIG. 4.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of theinvention. The drawing figures are not necessarily to scale. Certainfeatures of the embodiments may be shown exaggerated in scale or insomewhat schematic form and some details of conventional elements maynot be shown in the interest of clarity and conciseness. Although one ormore of these embodiments may be preferred, the embodiments disclosedshould not be interpreted, or otherwise used, as limiting the scope ofthe disclosure, including the claims. It is to be fully recognized thatthe different teachings of the embodiments discussed below may beemployed separately or in any suitable combination to produce desiredresults. In addition, one skilled in the art will understand that thefollowing description has broad application, and the discussion of anyembodiment is meant only to be exemplary of that embodiment, and notintended to intimate that the scope of the disclosure, including theclaims, is limited to that embodiment.

Certain terms are used throughout the following description and claimsto refer to particular features or components. As one skilled in the artwill appreciate, different persons may refer to the same feature orcomponent by different names. This document does not intend todistinguish between components or features that differ in name but notfunction. The drawing figures are not necessarily to scale. Certainfeatures and components herein may be shown exaggerated in scale or insomewhat schematic form and some details of conventional elements maynot be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . ” Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect connection. Thus, if a first device couples to a second device,that connection may be through a direct connection, or through anindirect connection via other devices, components, and connections. Inaddition, as used herein, the terms “axial” and “axially” generally meanalong or parallel to a central axis (e.g., central axis of a body or aport), while the terms “radial” and “radially” generally meanperpendicular to the central axis. For instance, an axial distancerefers to a distance measured along or parallel to the central axis, anda radial distance means a distance measured perpendicular to the centralaxis.

FIGS. 1A-1B show a drilling system 100 in accordance with variousembodiments. The drilling system 100 includes a platform of a drillingrig 126 with a riser string 122 and a blowout preventer stack 112 usedin oil and gas drilling operations connected to a wellhead housing 110.The wellhead housing 110 is disposed on the ocean floor and connectedwith the blowout preventer stack 112 with a hydraulic connector 114. Theblowout preventer stack 112 includes multiple blowout preventers 116 andkill and choke valves 118 in a vertical arrangement to control well borepressure in a manner known to those of skill in the art. Disposed on theupper end of the blowout preventer stack 112 is a riser adapter 120 toallow connection of the riser string 122 to the blowout preventer stack112. The riser string 122 is composed of multiple sections of pipe orriser joints 124 connected end to end and extending upwardly to thedrilling rig 126.

The drilling rig 126 further includes a moon pool 128 having atelescoping joint 130 disposed therein. The telescoping joint 130includes an inner barrel 132 that telescopes inside an outer barrel 134to allow relative motion between the drilling rig 126 and the wellheadhousing 110. A dual packer 135 is disposed at the upper end of the outerbarrel 134 and seals against the exterior of inner barrel 132. A landingtool adapter joint 136 is connected between the upper end of the riserstring 122 and the outer barrel 134 of the telescoping joint 130. Atension ring 138 is secured on the exterior of the outer barrel 134 andconnected by tension lines 140 to a hydraulic tensioning system as knownto those skilled in the art. This arrangement allows tension to beapplied by the hydraulic tensioning system to the tension ring 138 andthe telescoping joint 130. The tension is transmitted through thelanding tool adapter joint 136 to the riser string 122 to support theriser string 122. The upper end of the inner barrel 132 is terminated bya flex joint 142 and a diverter 144 connecting to a gimbal 146 and arotary table spider 148.

Before, and even after installation of the riser string 122 to thesubsea equipment, it may become necessary to detach the riser string 122from the diverter 144, the gimbal 146, rotary table 148, and any othersensitive equipment. For example, the drilling rig 126 may need to bemoved from one location to another and movement of the drilling rig 126relative to the riser would damage the equipment. In such cases, insteadof pulling up and dismantling the entire riser string 122, the drillingrig 126 may include a dynamic hang-off assembly 200 as shown in FIGS.2-6 to support the riser string 122 after it is detached from thediverter 144 and other equipment.

As shown in FIGS. 2-6, the dynamic hang-off assembly 200 includes thetension ring 138 that includes a housing 210 with a passage through thehousing 210. Alternatively, the housing 210 may be designed specificallyfor the hang-off assembly and replace the tension ring 138. The housing210 is connected by the tension lines 140 to a dynamic tensioning systemsuch as described above and as known to those skilled in the art. Thehousing 210 is shown as a ring but it should be appreciated that thehousing 210 may be any suitable shape to support the riser string 122.Although not shown connected in FIGS. 2-6, the tension lines 140 attachto the housing 210 at connection points 212 to support the housing 210in the moon pool 128.

The hang-off assembly 200 also includes an adapter 250 attachable to theriser string 122. The adapter 250 includes a profile 252 on the outsideof a radially extended portion of the adapter 250 as shown. It should beappreciated that the configuration of the adapter 250 and the profile252 shown are examples only and that different dimensions and locationsmay be used. The profile 252 is shown as annular but need not be formedcontinuously on the outside surface of the adapter 250. The adapterprofile 252 is shaped to enable the adapter 250 to be supported by thehousing 210 to support the riser string 122 as described below.

Shown in FIGS. 5A, 5B, and 6, the housing 210 further includes one ormore locking mechanisms 218 that engage the adapter profile 252 tosecure the adapter 250 to the housing 210. In some embodiments, thelocking mechanisms 218 are hydraulically operated. In other embodiments,the locking mechanisms 218 are mechanically operated. The lockingmechanisms 218 may be either hydraulically or mechanically operated insome embodiments. Shown in the figures are examples of hydraulicallyoperated locking mechanisms 218 that include a slide actuated betweenlocked and unlocked positions with a hydraulic piston. Additionalback-up or secondary locking mechanisms may also be included.

The hang-off assembly 200 is designed to be attached to the tensioningsystem on the drilling rig 126 to hang the riser string 122 through thedrilling rig moon pool 128. As shown, the riser string 122 and the flexjoint 142 are detached from the diverter 144, the gimbal 146, and therotary table spider 148. The riser adapter 250 is attached to the flexjoint 142 using a connection flange on the adapter 250. A riser stringrunning tool 300 is attached to the adapter 250 opposite the riserstring 122. The riser string running tool 300 is used on the drillingrig 126 to support and move the riser string 122 into position so thatthe riser string 122 can be supported by the hang-off assembly 200. Withthe housing 210 and the adapter 250 positioned as shown, the lockingmechanisms 218 are actuated to lock the adapter 250 to the housing 210.Once in position, the housing 210 thus secures the adapter 250 andsupports the riser 122 using the dynamic tensioning system on the rig126. This allows tension to be applied by the tensioning system to thehousing 210. The tension is transmitted through the housing 210 and theadapter 250 to the riser string 122 to support the riser string 122.With the riser string 122 locked in the dynamic hang-off assembly 200and supported by the tensioning system of the rig 126, the dynamichang-off assembly 200 is able to dynamically adjust to maintain tensionon the riser string 122. The rig 126 may now be moved to a differentlocation while the riser string 122 remains suspended through the moonpool 128.

Although the present invention has been described with respect tospecific details, it is not intended that such details should beregarded as limitations on the scope of the invention, except to theextent that they are included in the accompanying claims.

What is claimed is:
 1. A dynamic hang-off assembly for supporting ariser string from an off-shore drilling rig including a dynamictensioning system, including: a housing dynamically supportable by thetensioning system, the housing including a passage through the housing;an adapter positionable within the housing passage, the adapterincluding a profile on an outer surface, the riser string beingattachable to the adapter; the housing further including a lockingmechanism actuatable to engage the adapter profile and secure theadapter to the housing; wherein the assembly dynamically supports theriser string when the housing is supported by the tensioning system, theriser string is attached to the adapter, and the adapter is secured inthe housing.
 2. The dynamic hang-off assembly of claim 1, furthercomprising more than one locking mechanism.
 3. The dynamic hang-offassembly of claim 2, wherein the locking mechanisms are hydraulicallyactuated.
 4. The dynamic hang-off assembly of claim 1, wherein thehousing is ring-shaped.
 5. The dynamic hang-off assembly of claim 1,wherein the adapter profile extends around the outer surface of theadapter.
 6. The dynamic hang-off assembly of claim 1, wherein thehousing comprises a tension ring of the dynamic tensioning system.
 7. Anoff-shore drilling rig including: a platform including a moon pool; ariser string; a dynamic tensioning system; a dynamic hang-off assemblyincluding: a housing dynamically supportable by the tensioning system,the housing including a passage through the housing; an adapterpositionable within the housing passage, the adapter including a profileon an outer surface, the riser string being attachable to the adapter;and the housing further including a locking mechanism engageable withthe adapter profile to secure the adapter to the housing; and whereinthe assembly is capable of dynamically supporting the riser string. 8.The off-shore drilling rig of claim 7, further comprising more than onelocking mechanism.
 9. The off-shore drilling rig of claim 8, wherein thelocking mechanisms are hydraulically actuated.
 10. The off-shoredrilling rig of claim 7, wherein the housing is ring-shaped.
 11. Theoff-shore drilling rig of claim 7, wherein the adapter profile extendsaround the outer surface of the adapter.
 12. The off-shore drilling rigof claim 7, wherein the dynamic tensioning system comprises a tensionring and the tension ring comprises the housing of the dynamic hang-offassembly.
 13. A drilling system for an off-shore drilling rig including:a riser string; a dynamic tensioning system; a dynamic hang-off assemblyincluding: a housing dynamically supportable by the tensioning system,the housing including a passage through the housing; an adapterpositionable within the housing passage, the adapter including a profileon an outer surface, the riser string being attachable to the adapter;and the housing further including a locking mechanism engageable withthe adapter profile to secure the adapter to the housing; and whereinthe tensioning system is capable of dynamically supporting the riserstring.
 14. The system of claim 13, further comprising more than onelocking mechanism.
 15. The system of claim 15, wherein the lockingmechanisms are hydraulically actuated.
 16. The system of claim 13,wherein the housing is ring-shaped.
 17. The system of claim 13, whereinthe adapter profile extends around the outer surface of the adapter. 18.The system of claim 13, wherein the dynamic tensioning system comprisesa tension ring and the tension ring comprises the housing of the dynamichang-off assembly.